Thoughts on Wheel Setup

[ol84]

Im purchasing a complete rolling 70 SWB frame that is bagged on 4 corners with c notch, McGauphys 2" drop spindles, 5 lug disc front converted and 5 lug drum rear for a great deal. I am swapping my 67LWB to it. US Wheels has a blowout special on 20x9 with 4.75" backspacing. I want to run these on all 4 corners if possible. I have searched a lot of threads and see the small diameter steelies work with similar backspacing. Will these work as is or can I make them work with spacers or is it just a no go all together? Ive spent the better part of 6hrs trying to find a answer and the backspacings are all over the place. Any help might be appreciated. This was supposed the be a cheap project and I want to stay away from custom made wheels. Looking to stay with a smoothie/steelie style wheel.